In a traditional chuck which employs two-part jaws, each jaw comprises an adjustable carrier part to which is fixed a workpiece-engaging part. In order to accommodate a removable work-engaging part, the carrier has necessarily required a special form, often using a mating gear system with the work-engaging part. This special form prevented the use of more conventional jaws on a chuck so constructed.
Attachment or removal of such a specially designed work-engaging part entailed a precise matching of corresponding parts, and could be a time-consuming, exacting process.